Process for modifying the melting characteristics of a lignin

Abstract

The present invention is directed to a process for modifying the melting characteristics of a first lignin by chemically modifying the first lignin in a reactor under conditions of reduced temperature and increased pressure (e.g., greater than about one atmosphere). The process of modifying the melting characteristics of the first lignin can comprise (i) lowering the melting temperature of the first lignin; (ii) converting a partially meltable first lignin to a completely meltable second lignin; or (iii) reducing the melting viscosity of the first lignin.

1 . A process for modifying the melting characteristics of a first lignin, wherein the first lignin is a partially meltable lignin, a meltable lignin, or wherein the first lignin can be plasticized to become a partially meltable lignin or a meltable lignin; the process comprising:
 reacting said first lignin with a diol in a high-shear reactor to produce a second lignin;   wherein said diol is an aliphatic diol, an aromatic diol, or a diol of Formula (II):   
       
         
           
           
               
               
           
         
         wherein: 
         X 1  is independently, at each occurrence, selected from a chemical bond and —CHR X1 —; 
         X 2  is independently, at each occurrence, selected from a chemical bond and —CHR X2 —; 
         R X  is independently, at each occurrence, selected from —H, —C 1 -C 4  alkyl and —OH; 
         R X1  is independently, at each occurrence, selected from —H, —C 1 -C 4  alkyl and —OH; 
         R X2  is independently, at each occurrence, selected from —H, —C 1 -C 4  alkyl and —OH; and 
         n is any integer from 1 to 10,000; 
         wherein said second lignin is chemically modified by said diol. 
       
     
     
         2 . The process of  claim 1 , wherein the high-shear reactor is a screw reactor or a screw extruder, preferably wherein said high-shear reactor is a twin-screw extruder. 
     
     
         3 . The process of  any of the preceding claims , wherein said modifying the melting characteristics of the first lignin comprises (i) lowering the melting temperature of the first lignin; (ii) converting a partially meltable first lignin to a completely meltable second lignin; and/or (iii) reducing the melting viscosity of the first lignin. 
     
     
         4 . The process of  any of the preceding claims , wherein said chemical modification of said second lignin by said diol comprises etherification of said first lignin by said diol to produce an etherified second lignin. 
     
     
         5 . The process of  any of the preceding claims , wherein said first lignin and said diol are reacted in one or more reactive zones of said high shear reactor for about 2 seconds to about 20 minutes, preferably from about 30 seconds to about 5 minutes. 
     
     
         6 . The process of  any of the preceding claims , wherein the first lignin and the diol are reacted in the high-shear reactor at a temperature from about 50° C. to about 200° C.; preferably from about 70° C. to about 120° C. 
     
     
         7 . The process of  any of the preceding claims , wherein the first lignin and the diol are reacted in the high-shear reactor at a pressure from about 1.1 bar (0.11 MPa) to about 20 bar (2.0 MPa), preferably at a pressure from about 4 bar (0.4 MPa) to about 9 bar (0.9 MPa). 
     
     
         8 . The process of  any of the preceding claims , wherein the first lignin and the diol are reacted in the high-shear wherein the shear stress inside said high-shear reactor is from about 100 N/m 2  to about 10,000 N/m 2 . 
     
     
         9 . The process of  any of the preceding claims , wherein a hydroxyl group of said first lignin has not been previously chemically modified by reaction with a diol, preferably an aliphatic diol, an aromatic diol, or a diol of Formula (II); more preferably a diol of Formula II. 
     
     
         10 . The process of  any of the preceding claims , wherein at least 10% of the diol chemically reacts with the first lignin. 
     
     
         11 . The process of  any of the preceding claims , wherein the diol comprises between about 2% to about 60% of the total weight of the diol and first lignin; preferably about 5% to about 15% of the total weight of the diol and the first lignin. 
     
     
         12 . The process of  any of the preceding claims , wherein the diol is a diol of Formula (II). 
     
     
         13 . The process of  any of the preceding claims , wherein the first lignin is produced by separation of crude lignin from lignocellulose or by an additional process step on crude lignin to produce a lignin fraction or a lignin derivative, preferably wherein the separation process is a pulping process or a hydrolytic process, more preferably a kraft process producing kraft lignin, a soda process producing soda lignin, an organosolv process producing organosolv lignin or a sulphite process producing lignosulphonates. 
     
     
         14 . The process of any of  claims 1-13 , wherein the first lignin is produced by extraction of the soluble fraction of a hydrolytic lignin with an extraction solvent, preferably wherein the extraction solvent is also used for the pulping of lignin, preferably wherein the extraction solvent is aqueous sodium hydroxide or ethanol. 
     
     
         15 . The process of  any of the preceding claims , wherein the first lignin (i) is at least 70% pure as measured by Klason lignin; or (ii) has an aliphatic —OH content of at least 0.5 mmol/g. 
     
     
         16 . The process of  any of the preceding claims , wherein the first lignin is a plasticized lignin prepared by combining a crude lignin with a plasticizer, preferably wherein the plasticizer is PEGDM 250, PEGDM 500, ethylene carbonate, propylene carbonate, caprolactone, 1,4-diazabicyclo (2,2,2) octane, vanillin, acetosyringone, acetovanillone, ferulic acid, homovanilic acid, adipic acid, lactic acid, succinic acid, glycerol, or a combination thereof. 
     
     
         17 . The process of  any of the preceding claims , wherein the diol is selected from an aromatic diol, an aliphatic diol, a polyol, and a polyglycol; preferably wherein the aliphatic diol is selected from mono ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; preferably wherein the polyglycol is glycerol; and preferably wherein the polyglycol is selected from diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, polyethylene glycol, or polypropylene glycol, more preferably wherein said polyethylene glycol has a molecular weight of about 400 g/mol, 800 g/mol or 1200 g/mol, and wherein said polypropylene glycol has a molecular weight of about 400 g/mol, 725 g/mol, 1,000 g/mol, or 2,000 g/mol; or a combination thereof. 
     
     
         18 . A modified lignin, produced by a process according to any one of  claims 1-17 , comprising a structural unit of the formula: 
       
         
           
           
               
               
           
         
         wherein: 
         R is selected from C 1 -C 20  alkyl, —(CHR A —CHR B —O) n —H, and C 6 -C 14  aryl, wherein each alkyl or aryl is optionally substituted by one or more —OH; 
         n is an integer from 1 to 10,000; 
         R A  and R B  are each independently H or C 1 -C 6  alkyl; 
         R 1A  is H and R 1  is independently selected from —H, —OH, —O-lignin polymer residue, lignin polymer residue, and a carbohydrate; or R 1A  and R 1  combine together with the carbon atom to which they are attached to form a carbonyl group; 
         R 2A  is H and R 2  is independently selected from —H, —OH, —SH, —O-lignin polymer residue, lignin polymer residue, and a carbohydrate; or R 2A  and R 2  combine together with the carbon atom to which they are attached to form a carbonyl group; 
         R 3  is independently selected from —H, —OCH 3 , and lignin polymer residue; 
         R 4  is independently selected from —H and lignin polymer residue; and 
         R 5  is independently selected from —H, —OCH 3 , and lignin polymer residue. 
       
     
     
         19 . A modified lignin produced by a process according to any one of  claims 1-17 .